Two de novo GluN2B mutations affect multiple NMDAR-functions and instigate severe pediatric encephalopathy

eLife

Tali Garin-Shkolnik¹  Rikke Steensbjerre Møller²  Katrine M Johannesen²  Ido Carmi³  Shai Kellner³  Ronit Heinrich³  Shai Berlin³  Abeer Abbasi³  Moshe Giladi⁴  Yoni Haitin⁴  Tova Hershkovitz⁵ 

[1] Clalit health services, Tel Aviv, Israel;Department of Epilepsy Genetics and Personalized Treatment, the Danish Epilepsy Centre, Dianalund, Denmark;Institute for Regional Health Services, University of Southern Denmark, Odense, Denmark;Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel;Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel;Genetics Institute, Rambam medical center, Haifa, Israel;

关键词: GRIN;    encephalopathy;    ligand binding domain;    de novo mutation;    loss of function;    neurons;    Human;    Xenopus;   

DOI  :  10.7554/eLife.67555

来源: eLife Sciences Publications, Ltd

【 摘 要 】

The N-methyl-D-aspartate receptors (NMDARs; GluNRS) are glutamate receptors, commonly located at excitatory synapses. Mutations affecting receptor function often lead to devastating neurodevelopmental disorders. We have identified two toddlers with different heterozygous missense mutations of the same, and highly conserved, glycine residue located in the ligand-binding-domain of GRIN2B: G689C and G689S. Structure simulations suggest severely impaired glutamate binding, which we confirm by functional analysis. Both variants show three orders of magnitude reductions in glutamate EC50, with G689S exhibiting the largest reductions observed for GRIN2B (~2000-fold). Moreover, variants multimerize with, and upregulate, GluN2Bwt-subunits, thus engendering a strong dominant-negative effect on mixed channels. In neurons, overexpression of the variants instigates suppression of synaptic GluNRs. Lastly, while exploring spermine potentiation as a potential treatment, we discovered that the variants fail to respond due to G689’s novel role in proton-sensing. Together, we describe two unique variants with extreme effects on channel function. We employ protein-stability measures to explain why current (and future) LBD mutations in GluN2B primarily instigate Loss-of-Function.

【 授权许可】

CC BY